Due to amphibians’ unique integument and physiology, their metabolism and immune function is uniquely reliant on a stable environment. Infectious and nutritional diseases are common problems in tropical amphibians kept in suboptimal conditions. The range of temperatures necessary for proper metabolism, called the preferred optimal temperature zone (POTZ), varies among species. The POTZ of amphibian species is generally less than the POTZ of reptilians; caudatan species prefer temperatures substantially lower than anuran species. Water temperature regulation with water chillers and air conditioning must be considered for enclosures. Provision of a thermal gradient within a species POTZ allows most amphibians to self-regulate body temperature.
Enclosures should be spot-checked daily with a laser temperature probe, which can be purchased at most hardware or pet stores. Amphibians need moisture to prevent desiccation. Aquatic amphibians may be accommodated in aquariums with areas for swimming. Terrestrial amphibians need a shallow container of water in the enclosure. Moisture may also be provided by incorporating small streams, waterfalls, or ultrasonic humidifiers into enclosures, or by misting frequently with a spray bottle. Organic substrates and refugia that limit water loss can also help provide humidity within microhabitats.
Water must be clean and free of toxins such as chlorine, ammonia, nitrite, pesticides, and heavy metals. Chlorine can be removed from tap water by placing the water in a container and circulating it through a carbon filter for ≥ 24 hours before use. Some municipal water may include chloramines. The chloramine bond must be split with specific dechlorinating agents (eg, sodium thiosulfate), after which water can be filtered with carbon to remove the chlorine. External canister filters or under-gravel filters help maintain water quality in tank waterfalls, streams, and ponds.
Suitable substrates include gravel, soil, sphagnum moss, and mulch. Gravel should be either too large to be swallowed or small enough to be easily passed in the feces. Soils must be free of chemical additives such as fungicides. Heating soils to 93°C for 30 minutes is recommended to kill arthropods, such as trombiculid mites and helminth parasites. Untreated hardwood mulches and leaf litter can be used as substrate; however, cedar and pine mulches have toxic oils and should not be used. Some amphibians cannot tolerate low pH and may develop skin irritation if they come into contact with peat moss and sphagnum moss. Freezing substrates at < 0°C effectively removes many infectious organisms.
Adequate ventilation (1–2 fresh air changes per hour) is needed to prevent disease. Live plants are beneficial because they purify the air, remove organic wastes in the soil, filter light, generate humidity, and provide hiding and perching places. Aquatic plants oxygenate the water, remove nitrogenous waste, provide hiding places, and, often, provide a source of nutrition for larval amphibians.
Although the benefits of ultraviolet light are not well understood in amphibians, it is likely that diurnal species use ultraviolet B (UVB) light (280–320 nm) for calcium metabolism and for color rendition. Lights should be placed on a timer to mimic natural photoperiods. In nocturnal or photophobic species, dim light conditions as well as plenty of hiding places should be provided. Ultraviolet B bulbs must be changed every 6–8 months or according to the manufacturer’s specifications. Fluorescent or LED bulbs should be used to avoid heat production, and lighting must be within 18 in. of enclosure inhabitants. Glass attenuates the benefits of UVB light, and light sources therefore need to be placed to avoid this issue.
Household bleach (30 mL/L of water) can be used to disinfect tools and housing materials. A minimum of 30 minutes of contact time is recommended, after which tools should be thoroughly rinsed with fresh water and preferably dried before use. Commercial disinfectant products for animals can also be used.
Long-term maintenance of most captive amphibians requires live food. Although most adult terrestrial and aquatic amphibians feed on invertebrates, including earthworms, bloodworms, black worms, white worms, tubifex worms, springtails, fruit flies, fly larvae, mealworms, and crickets. Some amphibians feed on vertebrates and require live minnows, guppies, goldfish, or neonatal mice or rats. Vitamin and mineral supplements are necessary to prevent nutritional disease. These are commonly administered by gut loading insects, using commercially available diets high in calcium or by coating insects with powdered, multiple-vitamin preparations that include vitamin D3 and calcium (also known as dusting). Amphibians cannot synthesize carotenoids; therefore, they must be supplemented with a vitamin A source.
Quarantine for Amphibians
Quarantine is a preventive medicine practice that should be recommended to owners. Unfortunately, quarantine is often overlooked, leading to the introduction of disease into captive populations. The length of quarantine should be based on risk assessment of the collection and the source of the specimen; however, a 6- to 8-week period is typically adequate.
Veterinarians should do postmortem examination, and consider histologic evaluation, of amphibians that die in quarantine. During quarantine, regular veterinary visits should be scheduled and consist of at least an entrance and exit examination. Essential diagnostic evaluations to consider include parasitological examination of feces, water quality testing, skin scrapes of discolored or abnormal areas, PCR assay (eg, chytridiomycosis, ranavirus), gill biopsies, and blood work when large enough. Veterinarians should encourage owners to keep a log of the patient's appetite and behavior. Regular weight checks may be beneficial.
Quarantine enclosures should be easy to clean. A substrate of moist paper towel is adequate for most species, and plastic tubing, such as PVC, can be used for hiding places and perches for arboreal species. Disturbances should be kept to a minimum to reduce stress. Owners should use separate cleaning tools and consider changing clothes when moving between the care of quarantined animals and collection animals. Due to the risk of pathogenic pollution, all enclosure substrate and furniture must be thoroughly decontaminated prior to disposal. Humidifiers and spray bottles must be disinfected weekly to remove potentially pathogenic bacteria.
